The present invention relates to a cam device for the extraction and swinging of the front plate in a vertical sand molding machine, designed to prevent sudden changes in the movements of the plate during its displacement and swivelling, in order to allow the extraction of each sand mold and its prior conformation or molding.
The object of the invention is to provide a new cam device applicable to sand molding machines with the aforementioned object, in which the active surface of the cam faces downwards to prevent the deposit of sand or dirt between said cam and its supporting follower incorporated in the machine to achieve its swivelling.
Sand molding machines in which the production and output of the molds is in a vertical position are provided with a generally rectangular chamber in which the sand is blown through a hopper or bell placed on the top, which chamber is closed on one end by a displaceable and swinging plate which allows the exit of the molded mold, while the other end is closed by a rear plate associated to a compacting piston, which is also used to push on the mold and expel it in order to place said mold on the stack of previously produced molds.
The mold is obtained by blowing sand in the chamber, followed by compacting the sand with the combined press of both plates. After this the swinging plate is opened and swivelled to allow the mold to exit, which is achieved by pushing with the rear plate associated to the pushing piston. Thus the mold is extracted and placed on the previously obtained pile.
Currently, the swinging plate is opened and closed by a variety of driving mechanisms, among which may be mentioned one comprising a cam which rests by its top surface on a follower, so that said cam is connected to the swivelling plate to produce the swivelling of the plate as the cam moves and rests on the follower.
The arrangement of this cam with its active face facing upwards, and therefore with the follower on top results in sand being deposited between these elements which may damage the mechanism, and which thus require periodic cleanings to prevent this damage. Additionally, the known mechanisms which are based on the action of a cam are constructed such that there are sudden changes in the motion of the plate.
The device disclosed has been designed to solve the aforementioned problems by means of a simple yet effective solution, considering the loads supported by the device components to prevent sudden changes in the plate motion during its operation.
More specifically, the device of the invention comprises a cam with its active surface facing downwards, so that its follower is on the bottom and the formation and deposit of dirt between them is thereby prevented.
Said cam is jointed on one side to a frame which may move longitudinally, which in turn is jointed to the swivelling front plate, while on the other side the cam is jointed to a connecting rod, which is in turn jointed on its opposite end to the swinging plate. These joints of the aforementioned elements determine a cross-linkage of four bars by which the motion of the cam becomes a displacement and swivelling of the swinging front plate, thereby allowing the exit of the sand mold.
The moving frame connected to the cam is driven by interposing bars with a cylinder placed opposite the drive cylinder for the rear plate, producing a motion in either sense of the frame itself. Initially, a push of the cylinder will only cause the longitudinal displacement of the front plate and its extraction, until the cam reaches the follower, at which time if the cylinder continues to push the cam will begin to swivel, pushing the connecting rod and in turn the front plate, thus making the latter swing to allow exit of the mold.